Can’t buy output tubes anywhere except from manufacturers at high prices.

I thought it was always common knowledge the "Telefunken Black Label" tubes were just JJ’s. Always look at the shape of the glass dome (especially on EL34, for example) -- only JJ’s have that goofy, awkward rounded dome shape.

Viva Tubes has them. The prices are up but,  the price of everything is up now.. 

They've been out of KT120 and Gold Lion KT88 for a while now. And their supplies may be dwindling on remaining Russian KT88, EH KT90, and KT150. Mullard KT88 are still available for now (up to matched octets), and are excellent. Better get those while you can, if you're in need. I bought a couple octets for my VAC amps.

@weebeesdad

Yes, I have the Viva Mullard KT88 in my 200iQ’s right now. I’ve previously (this year) had both Gold Lion KT88 (stock from VAC) and Tung-Sol KT120 in these same amps. I haven’t directly compared the two, and I’m not going to say they sound exactly the same, but the KT88’s sound much more alike than different. I really like both! They are of equivalent quality. The KT120 sound more different, but also excellent -- they’re a bit meatier through parts of the midrange and bass. Incidentally, the KT150 were awful in these amps -- the bass was powerful and fun but overpowered the music. 

Anyways, I’m a fan of all 3 of these tubes! In my main system I have a pair of VAC Master 300 amps, with the stock KT88 Gold Lions. There are SIXTEEN of them, so I’m not gonna change them until I have to 😅